In addition to sterilizing and disinfecting foods and utensils, Ozone and other oxidizing gases are used to sterilize, disinfect or deodorize predetermined atmospheres such as hospital operating rooms. On the one hand, gases like ozone are extremely toxic and have an effect on the human body. On the other hand, however, the concentration of oxidants in the air is an important element for predicting photochemical smog levels. Consequently, various methods have been developed for monitoring and detecting these oxidizing gas concentrations. For example, a color change based on a reaction of the following formula (1) is primarily used to detect ozone.2KI+O→I2+K2OExamples of conventionally known detection methods using this principle include a method in which a gas containing ozone  is introduced into a potassium iodide solution followed by optically measuring the degree of a color change proportional to the amount of iodine formed with a calorimeter, and simpler methods using a detection tube.
In the above-mentioned optical detection method, the measuring method is complicated and a certain amount of time is required until detection. In addition, since the device itself is extremely expensive, huge costs are incurred particularly in the case of attempting to simultaneously measure ozone concentrations at multiple locations since a plurality of devices are required. In addition, in the case of using the above-mentioned detection tube, although the method is simpler than the above-mentioned optical method, it is still expensive, and it is necessary to aspirate oxidant either manually or automatically for each measurement.
Sterilization treatment is carried out for disinfecting and sterilizing various materials and instruments used in hospitals and research facilities. Known examples of this sterilization treatment include high-temperature steam sterilization, ethylene oxide gas sterilization and plasma sterilization treatment. Among these, plasma sterilization treatment sterilizes equipment and materials with low-temperature plasma by generating plasma in a hydrogen peroxide or other oxidizing gas atmosphere, and has the advantage of enabling sterilization at a comparatively low temperature. 
In this sterilization treatment as well, it is necessary to install an indicator to confirm whether or not the sterilization treatment has been completed in the same manner as other treatment methods. More specifically, it is necessary to install an indicator for determining the atmospheric gas concentration in the treatment system and exposure time within the plasma sterilization device.
A known example of a technology of the prior art relating to the above-mentioned indicator involves detection of sterilization treatment by a color change from blue to light yellow due to the action of peracetic acid or acetic acid gas by an indicator using a type of pH indicator in the form of bromphenol blue when monitoring a sterilization step in low-temperature plasma sterilization using a gas containing peracetic acid and acetic acid as the main components thereof (Patent Document 1: U.S. Pat. No. 5,482,684).
In addition, a plasma sterilization indicator is known which is composed of a pigment, a coloring assistant and a binder, and changes color as a result of plasma sterilization (Patent Document 2: Japanese Patent Application Publication No. H11-178904, Patent Document 3: Japanese Patent Application Publication No. 2002-11081).
Moreover, an ink composition for detecting plasma sterilization is known which contains an anthraquinone dye having at least one type of amino group among a primary amino group and secondary amino group (Patent Document 4: Japanese  Patent Application Publication No. 2001-174449).